Consideration is being given to applying organic EL elements, such as organic EL panels, as high-efficiency surface light sources to various types of devices. For example, applying organic EL elements to devices, such as lightning fixtures, displays, and windows, is being expected.
This type of organic EL element includes, for example, a translucent substrate, a transparent electrode made of, for example, indium tin oxide (ITO) and formed on the translucent substrate, an organic light emitting layer formed on the transparent electrode, and a reflecting electrode formed on the organic light emitting layer.
Transparent conductive materials such as ITO that are used as materials for transparent electrodes generally have high resistivity. Thus, if in the above organic EL element, voltage is applied from an electrode terminal portion (extraction electrode) provided in the peripheral portion to the transparent electrode (ITO), light emission luminance in the central region of the light emitting surface, which is far from the electrode terminal portion, decreases due to a voltage drop across the transparent electrode. As a result, unevenness in luminance occurs at the light emitting surface of the organic EL element.
In view of this, technology is known in which a thin linear auxiliary electrode made of a low-resistance material, such as a metal, is formed in a grid-like pattern on the transparent electrode so as to suppress unevenness in the luminance of the light emitting surface, which is caused by a voltage drop across the transparent electrode (e.g., Patent Literature (PTL) 1).